Second build - Steel heavy gantry machine for aluminium

[lukahr]

After completing my 1st build and using machine for more than 3 years i have come to point where i need upgrade.
My first machine was intended mainly for wood and some light aluminium cutting and now machine is only working aluminium and some rare light wood cutting
1st build was all aluminium and now i'm having some troubles with vibrations and rigidity of machine. But still i'm cutting parts out of aluminium in tolerances of 0.05mm which is good for machine not intended for this type of work.
1st machine photo and some parts


Second machine will be all steel maybe some parts from EG or solid granite.
I'm liking design from Datron MxCube so this will be some kind of mock-up from that and my ideas. (also i have friend who work in granite machining center, so that can help )
Plan is to build machine capable of milling aluminium parts without any problems with good tolerances 0.01mm.

So i'm aiming for working area of 1000x1000x300mm
Welded structure filled with sand or EG. (cca 500kg)
Gantry - steel EG combination cca 150-200kg
profile rails 25mm on all axes
20mm-25mm ballscrews on all axes probably with 10mm pitch.
Double ballscrew on Y axis.
Servo motors, looking on DMM 400W set, but i dont know if this will be enough for gantry of this weight.
Probably teknomotor spindle, still deciding if i should go ATC or not.

So i have started designing cad and i have come to my first dilemma.

Gantry beam is 120x220mm steel tube wall thicknes 12.5mm (80kg)
I'm deciding should i build gantry sides like left or right side.



left - solid block of epoxy-granite with embedded steel plate for bearing and gantry to bolt on .
right - hollow welded steel side out of 10mm steel sheet

weigh of both is pretty much the same (20kg) but i think that vibration dampening will be better on left side.
This will be project for next year so now i'm in cad phase. So any input in design will be appreciated.

What so you guys think ?

Luka

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[peteeng]

Hi Luka - Sounds like its time for a pull down and rebuild if your getting vibs. Bearings need checking after some time. If you can go granite I'd work on that. But remember vibs do not come from the structure they are driven from the motors or the tool. So isolate motors from the structure and the spindle holder....Peter

[lukahr]

Yes i think that too.
I'm suspecting my spindle bearing and overall structure of z axis.

Yes i have decided to go with granite or EG, this will also be easier for me to build as i'm not good with welding and all post welding operations will cost me in the end more than casting EG.
As i'm in Europe i have pretty easy access to Silimix 282 - i'll probably use that. (I need to calculate if it's worth mixing aggregate by myself)

But now after reading for some time about C-frame, Bridge and Gantry designs i'm really not sure what i want
If i'm rebuilding cnc I would like to make machine that will be versatile and good for all possible work that i will be doing.
That including milling steel.

At first my requirement was worktable of 1000x1000mm (that would be possible with Gantry design) but i think that will not be possible if i want to mill steel as i'm reading that Gantrys are not good for steel.
Everyone is saying that if i want to mill steel i need fixed bridge or C style VMC.

For spindle i'm thinking i should go with double spindles, one for steels and other for all other softer materials.
one BT30 + servo and second High speed 2.2kw 24000 (i already have this one)

Luka

[peteeng]

Hi Lukahr - Gantries are used for steel just they need to be very very stiff probably 200x200x12 at least in steel. Look at a moving column design... I'm designing an epoxy high modulus fibre moving gantry mill at the moment...Peter

I expect your machine to have a moving control cabinet as well....

https://www.industrialmachinery.net....moving-column/

"Epoxy-Granite machine bases (was Polymer concrete frame?)" look at the last pages of this thread for info on epoxy granite

all my reading and calculations say that good sand and epoxy is as good as the graded approach. Keep it simple.


shrink this one down...

[lukahr]

I'll check what aggregates are needed for good EG mix and if i can source them localy.
Drying sand is really no problem for me as i have at home industrial wood drying kiln machine.

I'm not so fond of this moving column design. I think it is really hard to get good stability of moving column looking like skyscraper
If bearing blocks would be more wide apart on the bottom - maybe.
Or design like this DMG machine this one looks solid.

[peteeng]

Hi Lukahr - Yes extremely solid. I do intend to space the column bearings further apart. The DMC machine still has a saddle and that's something I wanted to get rid of. But you have me thinking.... a static table has advantages as well.... Peter

[lukahr]

Yea i'm fan of static table and CNC that i own now has static table and i'm really liking it.

Regarding my design now it has totally shifted over
Here is a design sketch that i'm working on now.
I decided that i will go with 1x1m work-space and welded base filled EG or polymerconcrete.



This will be heavy machine.
I'm planing to mill steel with it so it need to be rigid.

Main vertical columns are 150x150mm, all others 150x100mm 6mm thick.

Now i'm deciding on choosing linear rails and blocks.
I'm deciding between
BST motion - HIWIN ball bearing size 35 or 30mm
TBI motion - HIWIN roller bearnig size 25 or 30mm

Price is actually very close so i dont really know what to pick, bigger ball block or smaller roller blocks .
Also BST motion has good reputation, for TBI motion i'm not sure .

I'm going for at least medium pre-load if not high preload.

Luka

[teamloks1]

im using hiwin roller RGW model now i think its pretty silent compare to ball

[lukahr]

im using hiwin roller RGW model now i think its pretty silent compare to ball

What about rigidity ? roller type should be better than ball
Where did you buy yours ?

Yes i have looked at same model RGW - with flange, preload ZA (medium) and H accuracy size 30mm

https://www.aliexpress.com/item/3289...7fdd5956HKl7bw

They have both RGW and RGH models but i like flange unit more as mounting bolts are bigger m10 comparte to m8 on HGH.
I

[mactec54]

Yea i'm fan of static table and CNC that i own now has static table and i'm really liking it.

Regarding my design now it has totally shifted over
Here is a design sketch that i'm working on now.
I decided that i will go with 1x1m work-space and welded base filled EG or polymerconcrete.



This will be heavy machine.
I'm planing to mill steel with it so it need to be rigid.

Main vertical columns are 150x150mm, all others 150x100mm 6mm thick.

Now i'm deciding on choosing linear rails and blocks.
I'm deciding between
BST motion - HIWIN ball bearing size 35 or 30mm
TBI motion - HIWIN roller bearnig size 25 or 30mm

Price is actually very close so i dont really know what to pick, bigger ball block or smaller roller blocks .
Also BST motion has good reputation, for TBI motion i'm not sure .

I'm going for at least medium pre-load if not high preload.

Luka

Looks good filled with EG should work well, your weakest link will always be the Z axes so a lot of focuses on that part will give you a very well build machine

Make sure you can machine the Rail mounting faces

[teamloks1]

What about rigidity ? roller type should be better than ball
Where did you buy yours ?

Yes i have looked at same model RGW - with flange, preload ZA (medium) and H accuracy size 30mm

https://www.aliexpress.com/item/3289...7fdd5956HKl7bw

They have both RGW and RGH models but i like flange unit more as mounting bolts are bigger m10 comparte to m8 on HGH.
I

since im from malaysia i bought directly from taiwan this is the model i bought

RGW25HA2R3000ZAH+KK 2 UNIT
RGW25HA2R2400ZAH+KK 2 UNIT
RGW25HA2R550ZAH+KK 2 UNIT

im ordering custom with double seal and scrapper

that cost me around 880 usd for 6rail and 12 block

[lukahr]

Looks good filled with EG should work well, your weakest link will always be the Z axes so a lot of focuses on that part will give you a very well build machine

Make sure you can machine the Rail mounting faces

Yes whole machine will be filled.

I'm planing to make something similar to this design. I will also use pneumatic counterbalance on z axis.


Marked with red will be position of my servomotor spindle 2.2KW (30 minutes 3.7kw) 12000rpm



All mounting faces will be milled in company that will weld frame for me.
After transport to my place and finding right place to put this heavy machine whole think will be filled with EG or Polymerconcrete.
So no more moving machine after filling. (it will be to heavy anyway)

[lukahr]

since im from malaysia i bought directly from taiwan this is the model i bought

RGW25HA2R3000ZAH+KK 2 UNIT
RGW25HA2R2400ZAH+KK 2 UNIT
RGW25HA2R550ZAH+KK 2 UNIT

im ordering custom with double seal and scrapper

that cost me around 880 usd for 6rail and 12 block

Ok that is really good price,
You have blocks rated super heavy with medium preload and high precision option with addition of double seal and scrapper.
What are the ballscrews you use ?

[teamloks1]

Ok that is really good price,
You have blocks rated super heavy with medium preload and high precision option with addition of double seal and scrapper.
What are the ballscrews you use ?

yes anyway this is router im going to make still thinking hard about frame. i use RFBY2525 rotary ballnut from TBI

[lukahr]

I'm looking for my ballscrews, and i'm loking TBI brand diameter 25mm step 5mm or 10mm.

I see they have rolled c5 and ground c5 , what is the difference in accuracy if both are c5 should be same, or not?

[teamloks1]

I'm looking for my ballscrews, and i'm loking TBI brand diameter 25mm step 5mm or 10mm.

I see they have rolled c5 and ground c5 , what is the difference in accuracy if both are c5 should be same, or not?

im not sure about it im using ground c5 double nut for my z axis this cost me 150usd with bk15 c5 angular+bf15 seat

[lukahr]

im not sure about it im using ground c5 double nut for my z axis this cost me 150usd with bk15 c5 angular+bf15 seat

Nice little setup you have there.

Do you maybe know what series is this ballnut ? OFI&DFI ?


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[peteeng]

200x200x13 is 9724mm2 so its 9724*1000*2700e-9= 26.5kg/m so they want 136/26.5= 5.13USD per metre ie $7.70AUD per metre yes that's a very good price compared to my local prices in Oz for short length (about $10AUD/kg here). Wouldn't use the 100x100 too small and the 200x200 gives you good room for bearings. 13mm is good for threads. Use it for other areas as well. Good section. Cheers Peter S

yeah error 403 seems to be gone.. Peter

[teamloks1]

Nice little setup you have there.

Do you maybe know what series is this ballnut ? OFI&DFI ?


Sent from my iPhone using Tapatalk

its OFU